The present invention relates to a suspension frame construction for supporting a suspension lower arm, an engine mounting member, and the like.
Generally, the vehicle body constructions of motor vehicles are broadly divided into a framed construction used for motor trucks and the like and a frameless construction used for passenger cars and the like. The frameless construction incorporates side members and cross members as a part of body in place of a frame to increase the torsional rigidity. A chassis part is usually attached directly to the body, but, on some vehicles, it is attached to a partial frame, what is called a subframe, and then is assembled to the body.
The subframe is also referred to as a suspension frame because suspension lower arms are usually attached to both sides of the subframe. Hereafter, the subframe and the like are given a general name of a suspension frame.
The suspension frame is assembled to the vehicle body as an assembled part after a suspension lower frame, a stabilizer, and the like are attached thereto. The suspension frame is generally composed of an upper plate, a lower plate, and lower arm mounting brackets as a basic construction.
FIGS. 9 to 11 show a construction of a conventional suspension frame (Japanese Patent Provisional Publication No. 7-179180).
A suspension frame 100 is supported on a pair of side members 101, 101 at both sides thereof, and suspension lower arms 102, 102 are attached to both sides of the suspension frame 100. Between the suspension frame 100 and a cross member 103 installed on the front is provided a center member 104, to which an engine 105 is assembled.
The suspension frame 100 is usually disposed at the lower part of an engine room isolated by a dash panel 106, and is fitted with various fittings. The dash panel 106 is fitted with a steering knuckle 107 via brackets 108.
As shown in FIGS. 12 to 14, the suspension frame 100 is formed by joining an upper plate 109 and a lower plate 110, which are formed by pressing a steel plate etc., by welding or other means, and at both sides, right and left, of the suspension frame 100 are provided vehicle body mounting portions h, i and j, and in the central portion thereof are provided engine mounting member mounting portions k. At both sides in the vehicle width direction of the suspension frame 100, a pair of suspension lower arm mounting portions 100a and 100d are provided. In the suspension lower arm mounting portion 100a on the front side of the vehicle body is provided a lower arm mounting bracket 111 in a cantilever state.
The lower arm mounting bracket 111 is formed substantially into a square box shape with one side being open by pressing or other means, and the opposed wall faces 111a and 111b thereof are provided with pivotally supporting portions 112, 112 for the suspension lower arms 102, 102. This lower arm mounting bracket 111, which is supported on the outside of the vehicle body mounting portions h, i and j in a cantilever manner, has a construction that provides low rigidity and is disadvantageous in terms of driving stability and vibration noise.
To mount the lower arm mounting bracket 111, as shown in FIG. 14, a distal end portion 109a of the upper plate 109 is lapped partially on and joined to the upper face of the lower arm mounting bracket 111. Also, the distal end of the lower plate 110 is butt-welded to the wall face of the lower arm mounting bracket 111. Therefore, a reinforcement 113 is installed between the upper plate 109 and the lower plate 110 to reinforce the mounting portion of the lower arm mounting bracket 111. Further, a flange portion 114 is provided along the open end portion of the lower arm mounting bracket 111 to increase the rigidity of the bracket 111.
The suspension frame 100 is subjected to the severest condition when a longitudinal load is applied thereto (for an actual vehicle, for example, when the brake is applied or when a wheel falls into a pothole).
When a braking load is applied to the suspension frame 100, as shown in FIG. 15, the mounting portion 100a of the lower arm mounting bracket 111 is put into a deformation mode of being opened to the outside while being twisted as indicated by the arrow {circle around (1)}, and a central portion 100b of the suspension frame 100 is put into a deformation mode of being sunk as indicated by the broken line {circle around (2)}.
The central portion 100b of the suspension frame 100 is also sunk in the same manner by a load applied by the engine mounting member at the time of sudden start.
On the other hand, as shown in FIG. 16, when a load is applied in the lateral direction, the mounting portion 100a of the lower arm mounting bracket 111 is twisted to the inside as indicated by the arrow {circle around (3)}. As a result, one of the lower arm mounting portions 100d on the vehicle body rear side of the suspension frame 100 is deformed upward as indicated by the arrow {circle around (4)}and the other thereof is deformed downward as indicated by the arrow {circle around (5)}. Also, on both sides of the central portion 100b of the suspension frame 100, one side is deformed upward as indicated by the arrow {circle around (4)}and the other side is deformed downward as indicated by the arrow {circle around (5)}. Thus, the suspension frame 100 is put into a deformation mode of being wavy.
As is apparent from the above-described deformation modes, the rigidity around the opening portion of the lower arm mounting bracket 111 is low in the case where the suspension frame 100 is formed merely by two upper and lower plates joined to each other. Near the opening portion, the vehicle body mounting portions lie. If the rigidity of this portion of the suspension frame 100 is low, therefore, there is a possibility that the first-order natural frequency of the suspension frame 100 resonates with the vehicle body.
The present invention has been made to solve the above problems, and accordingly an object thereof is to provide a suspension frame construction capable of increasing rigidity when a braking load, a lateral load, or an engine mounting load is applied to a suspension frame.
To solve the above problems, the present invention provides a suspension frame construction comprising an upper plate and a lower plate joined to each other to form a suspension frame; and front- and rear-side suspension lower arm support portions provided at both ends, right and left, of the suspension frame, wherein the rear-side suspension lower arm support portion is formed by opposing the upper plate and lower plate to each other at a fixed distance and a rear-side arm portion of a suspension lower arm is pivotally supported between the opposed portion of the upper plate and lower plate, and a reinforcing wall portion for connecting the upper plate and lower plate to each other is provided on the proximal end side of the pivotally supporting portion.
Also, the present invention provides a suspension frame construction comprising an upper plate and a lower plate joined to each other to form a suspension frame; and suspension lower arm support portions extending to substantially front and lateral sides, which is provided at both ends, right and left, of the suspension frame, wherein an outer wall portion is formed in the suspension lower arm support portion extending to substantially front side, and a reinforcing wall portion continuous with the outer wall portion is provided at the proximal end of the lateral-side extending portion provided on the rear end side of the outer wall portion.
Further, the present invention provides a suspension frame construction comprising an upper plate and a lower plate joined to each other to form a suspension frame; and front- and rear-side suspension lower arm support portions provided at both ends, right and left, of the suspension frame, wherein the rear-side suspension lower arm support portion is formed by opposing the upper plate and lower plate to each other at a fixed distance and a rear-side arm portion of a suspension lower arm is pivotally supported by a vertical shaft between the opposed portion of the upper plate and lower plate, and a reinforcing wall portion for connecting the upper plate and lower plate to each other is provided on the proximal end side of the pivotally supporting portion.